As part of the CE Header project from the CE Skills course , I needed to learn to work with DS7505. I used a Bus Pirate (Dangerous Prototypes) and probes, from Seeed Studio, to iteratively poke at it until I understood how to talk to it via I2C.
Once I soldered the DS7505 to a small carrier board from Adafruit, I placed it on a breadboard and wired it up to the Bus Pirate. Please note, the cable and connectors in the image below are from the Seeed probe cable. Some of the other probe cables have the colors in a different order on the connectors.
I used putty to connect to the Bus Pirate via a mini usb cable.
| Command | What it does |
| m 4 1 | Mode, I2C, Speed 5khz |
| W | Turn power on |
| P | Turn on pull ups |
| Command | What it does | Output |
| (1) | Find the slave address | 0x90(0x48 W) 0x91(0x48 R) |
| Command | What it does | Output |
| [ 0x90 0x01 [ 0x91 r:1 ] | Read the register | 0x00 (default) |
| [ 0x90 0x01 0x60 ] | Enable 12 bit resolution | |
| [ 0x90 0x01 0x60 [ 0x91 r:1 ] | Enable 12 bit resolution and read back current config | 0x60 |
| Command | What it does | Output |
| [ 0x90 0x00 [ 0x91 r:2 ] | Read the register | ex: 0x19 0xE0 |
|
How to calculate given: 0x19 0xE0 and 12 bit resolution. Bit 8 of MSB is the sign. 0=+ and 1=- The most significant 4 bits of the LSB are used for 12bit precision. |
MSB 0011001 25C + Total = 25.75C |
LSB 1100000 12/16=.75 |
| Given: 0xE6 0x78
Note: negative due to the 8th bit of the MSB being 1 |
MSB 11100110 (NOT 11100110) +1 00011001 + 1 00011010 -26C + Total = -25.0625C |
LSB 1111000
15/16=.9375 0.9375 |
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